package com.leetcode.demo;

/**
 * @author wangxiyuan
 * @description 将两个升序链表合并为一个新的 升序 链表并返回。新链表是通过拼接给定的两个链表的所有节点组成的。
 * 链表的遍历
 * @createDate 2021/8/23 12:00
 **/
public class Question21 {

    public class ListNode {
       int val;
       ListNode next;
       ListNode() {}
       ListNode(int val) { this.val = val; }
       ListNode(int val, ListNode next) { this.val = val; this.next = next; }
   }

   public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
      // 类似归并排序中的合并过程
      ListNode dummyHead = new ListNode(0);
      ListNode cur = dummyHead;
      while (l1 != null && l2 != null) {
         if (l1.val < l2.val) {
            cur.next = l1;
            l1 = l1.next;
         } else {
            cur.next = l2;
            l2 = l2.next;
         }
         cur = cur.next;
      }
      // 任一为空，直接连接另一条链表
      if (l1 == null) {
         cur.next = l2;
      } else {
         cur.next = l1;
      }
      return dummyHead.next;
   }
}
